This invention relates generally to projectors, and more particularly to projectors that are configured as a network of projectors.
The most exploited characteristics of a projector are its ability to display images that are larger in size than images produced by its CRT and LCD counterpart devices, and to place the images on arbitrary surfaces at a distance from projector. Like CRT and LCD based devices, projectors normally display flat, rectangular images. Unfortunately, many characteristics unique to projector-based displays are largely unexploited.
Because the projector is decoupled from the display surface, which is not the case in CRT or LCD devices, the size of the projector can be much smaller than the size of the image it produces. Overlapping images from multiple projectors could be effectively superimposed on the display surface, and images from projectors with very different specifications and form factors could be blended together. In addition, the display surface does not need to be planar or rigid, thus, many types of surfaces and merged projected images could be use to augment a physical environment.
Projector Trends
Projectors are getting smaller, lighter, brighter and cheaper. When devices get smaller, the flexibility in form factor spawns new modes of use and new applications. For example, future projectors could be used either in at fixed location or in a mobile setup.
Distributed, Commoditized Computing Trends
More and more, computation is distributed over clusters of heterogeneous, self-sufficient computing units rather than a set of well-organized mainframes. Advances in cheaper, more powerful computers accelerate this trend.
Similarly, in the projector system, it is desired to move away from large, monolithic, homogeneous systems to a network made up of heterogeneous, and self-sufficient projectors. Such projectors could be used in stand-alone mode, similar to PCs or PDAs, or operate cooperatively in clusters, similar to computing grids.
In the last few years, projectors have broken out of their traditional roles in entertainment, flight simulator, and presentation applications. Consequently, advances in projector-based systems are receiving greater attention, and projectors are started to be used for unconventional purposes.
Projector-Based Environments
Recently, display devices that augment the physical environment have become more popular, e.g., large monitors, projected screens, LCD or plasma screens for fixed installations, and handheld PDAs for mobile applications. Immersion is not a necessary goal of most of these displays.
Due to their shrinking size and cost, projectors are increasingly replacing traditional display devices and mediums, see Raskar et al., xe2x80x9cMultiprojector Displays using Camera-based Registration,xe2x80x9d IEEE Visualization, 1999, Underkoffler et al., xe2x80x9cEmancipated pixels: realworld graphics in the luminous room,xe2x80x9d SIGGRAPH 99 Conference Proceedings, pp., 385-392, 1999, Pinhanez, xe2x80x9cThe Everywhere Displays Projector: A Device to Create Ubiquitous Graphical Interfaces,xe2x80x9d Ubiquitous Computing, Ubicomp ""01, 2001, Sukthankar et al., xe2x80x9cScalable Alignment of Large-Format Multi-Projector Displays Using Camera Homography Trees,xe2x80x9d Proceedings of Visualization, 2002, and Stork, xe2x80x9cProjection-based Augmented Reality in Engineering Applications, 2002.
From a geometric point of view, those prior art projector systems use one or more environmental sensors assisting a central processing unit. The processing unit computes the Euclidean or affine relationships between a projector and a display surface.
In contrast, it is desired to provide a decentralized projector system based on individual self-contained projectors.
Some prior art projector systems provide automatic registration for seamless displays using a cluster of projectors, see Yang, xe2x80x9cPixelFlex:A Reconfigurable Multi-Projector Display System,xe2x80x9d IEEE Visualization 01, 2001, and Brown at al., xe2x80x9cA Practical and Flexible Large Format Display system,xe2x80x9d The Tenth Pacific Conference on Computer Graphics and Applications, pp. 178-183, 2002. However, those systems require environmental sensors, do not admit projectors beyond the range of any one sensor, and work only for first order planar surfaces.
It is desired to provide a projector that can display images on higher order surfaces such as cylinders and domes, without the use of environmental sensors.
Enhanced Projectors
Some prior art display systems use enhanced sensors and additional computation, see the xe2x80x9cI/O bulbxe2x80x9d as described by Underkoffler et al., above, which uses a co-located projector and camera. A tilt sensor can be used for automatic keystone correction, see Raskar, xe2x80x9cA Self Correcting Projector,xe2x80x9d IEEE Computer Vision and Pattern Recognition, 2001.
It is further desired to provide projectors with network capabilities, and to make projectors geometrically aware and self-configurable, so that projectors can communicate with each other, and be sensitive to the physical shape of display surfaces and objects present in the environment.
The invention provides a novel techniques that support a geometrically aware projector and self-configurable display systems composed of one or more of these geometrically aware projectors.
The invention also provides calibration and rendering techniques for displaying images on different types of surfaces and objects, in the presence of other projectors.
These techniques can be applied to traditional projector-based environments, and enable new types of applications and interfaces.
Therefore, it is an object of the invention to provide a shape-adaptive projector system. The shape adaptive, or geometrically aware projector displays images on planar or non-planar surface with minimum local distortion. The system handles a corresponding conformal projection problem, and variations to horizontal and vertical constraints.
It is also an object of the invention to provide a self-configuring ad-hoc projector cluster that can render what appears to be a single seamless image from multiple images projected by self-contained projectors, without using any environmental sensors.
It is an object of the invention to provide a method for globally aligning multiple images using master and Euclidean information for a scene. This includes a method for determining a largest inscribed rectangular image in a union of projected quadrilateral images, that is an arbitrarily shaped polygon.
It is an object of the invention to provide a projector system for displaying images on a curved display surfaces, specifically quadric surfaces. Therefore, a simplified parameterized transfer method is provided. To handle curved surfaces, the invention also provides a method for global aligning and registering images in the presence of small errors in pair-wise relationships due to distortion of projected images on curved surfaces.